FEMALE ENDOCRINE CONTROL MECHANISMS DURING THE NEONATAL PERIOD

Abstract

ABSTRACT The present investigations deal with the in vivo effect of different doses of exogenous LH on the RNA- and protein-synthesis in the cerebral cortex, hypothalamus, pituitary, liver, ovary, uterus and adrenal gland of newborn guinea pigs. An increase of 3H-uridine and 3H-leucine incorporation was noted only in the ovary and the uterus. All the other organs showed no response. As early as 1 hour after the injection, LH induced a statistically significant stimulation of amino-acid incorporation into the proteins of the ovary. 2 hours later similar observations were made on the uterus reflecting an induction of uterotrophic steroid biosynthesis in the ovary in response to LH. The lowest effective dose was 5 IU LH/100 g body weight. Furthermore the experiments gave evidence for the dependence of oestrogen synthesis on the ovarian protein formation. The experimental data support the assumption that the ovary of newborn animals is not refractory to stimulation by gonadotrophic hormones. The ovary of newborn guinea pigs shows a relatively low sensitivity against RNA- and protein-synthesis inhibiting substances such as actinomycin and cycloheximide as compared to the liver. The mode of action of LH on the ovary seems to be identical during post partum life and advancing sexual maturation. The existing ovarian gonadotrophin sensitivity indicates that the hypothalamus or possibly the pituitary is primarily responsible for the functional immaturity of the endocrine ovarian control mechanisms during the neonatal period. The restricted functional capacity of the neonatal hypothalamus is characterized by the resistence of this organ to hormones regulating the hypothalamic endocrine function via short and long feedback mechanisms.